This article is an axiomatic approach to the problem of ranking game forms in terms of the predictability they offer to individuals. Two criteria are proposed and characterized, the CardMin and the CardMax. Both compare game forms on the basis of the number of distinct outcomes that can result from the choice of a CardMin (resp. CardMax) strategy. The CardMin (resp. CardMax) strategy is defined as a strategy leading to the smallest (resp. highest) number of different outcomes. In both cases, the lower these numbers the better the game form.